With all the out of the ordinary excitement and taking communication cues from their humans, it is possible that dogs can feel depressed after the holidays. From the article “Dogs Can Feel Post-Holiday Letdown“:
“It’s not unusual for dogs to feel down, particularly in times of change, writes veterinarian Bonnie Beaver at webmd.com. John Ciribassi, past president of the American Veterinary Society of Animal Behavior, also at webmd.com says the “blues” can include less activity and socializing with humans or animals, and eating and sleeping habits can change.”
The full article is insightful and may help explain why your fur-kid may seem out of sorts this week.